Hyperlipidaemia has been recognized as the major risk factor in causing cardiovascular diseases due to atherosclerosis. Atherosclerosis and other such peripheral vascular diseases affect the quality of life of a large population in the world. The emphasis during the therapy is laid on lowering the elevated plasma LDL cholesterol, low-density lipoprotein and plasma triglycerides in order to prevent or reduce the risk of occurrence of cardiovascular diseases. The details of etiology in atherosclerosis and coronary artery diseases is discussed by Ross and Glomset [New Engl. J. Med., 295, 369-377 (1976)]. Plasma cholesterol is generally esterified with various serum lipoproteins and numerous studies suggest an inverse relation between serum HDL-cholesterol level and risk for occurrence of cardiovascular disease. Many studies have suggests an increased risk of coronary artery diseases (CAD) due to elevated LDL and VLDL-cholesterol levels [Stampfer et al., N. Engl. J. Med., 325, 373-381(1991)]. The other studies illustrate protective effects of HDL against progression of atherosclerosis. Thus, HDL has become a crucial factor in treating diseases with increased levels of cholesterol [Miller et. al., Br. Med. J. 282, 1741-1744(1981); Picardo et al., Arteriosclerosis, 6, 434-441 (1986); Macikinnon et al., J. Biol. Chem. 261, 2548-2552 (1986)].
Diabetes is associated with a number of complications and also affects a large population. Usually, the disease is closely associated with other diseases such as obesity, hyperlipidemia, hypertension and angina. It is a well recognized that improper treatment aggravates impaired glucose tolerance and insulin resistance, leading to frank diabetes. Further, patients with insulin resistance and type 2 diabetes often have raised triglycerides and low HDL-cholesterol concentrations and therefore, have greater risk of cardiovascular diseases. The present therapy mostly includes sulfonylureas and biguamides along with insulin. This drug therapy have limitations such as mild to severe hypoglycemia, which may lead to coma or in some cases may lead to death. The later mainly results due to unsatisfactory glycaemic control. The recent addition of thiazolidinediones, drugs having insulin-sensitizing action. Thiazolidinediones are prescribed alone or in combination with other anti-diabetic agents like troglitazone, rosiglitazone and pioglitazone. These are useful in treating diabetes, affects lipid metabolism but are suspected to have tumor-inducing potential and cause hepatic dysfunction, which may lead to liver failure. Further, serious undesirable side-effects have occurred in animal and/or human studies including cardiac hypertrophy, hema dilution and liver toxicity in a few glitazones progressing to advanced human trials. The drawback is considered to be idiosyncratic. Presently, there is need for a safe and an effective drug, to treat insulin resistance, diabetes and hyperlipidemia.
Obesity is another major health problem being associated with increased morbidity and mortality. It is a metabolic disorder, in which excess of fat is accumulated in the body. Although, its etiology is unclear, the general feature includes excess of calorie intake than it is consumed. Various therapies such as dieting, exercise, appetite suppression, inhibition of fat absorption etc. have been used to combat obesity. However, more efficient therapies to treat this abnormality is essential as obesity is closely related to several diseases such as coronary heart disease, stroke, diabetes, gout, osteoarthritis, hyperlipidaemia and reduced fertility. It also leads to social and psychological problems.
Peroxisome Proliferator Activated Receptor (PPAR) is a member of the steroid/retinoid/thyroid hormone receptor family. PPARα, PPARγ and PPARδ have been identified as subtypes of PPARs. Extensive reviews regarding PPAR, their role in different diseased conditions are widely published [Endocrine Reviews, 20(5), 649-688 (1999); J. Medicinal Chemistry, 43(4), 58-550 (2000); Cell, 55, 932-943 (1999); Nature, 405, 421-424 (2000); Trends in pharmacological Sci., 469-473 (2000)]. PPARγ activation has been found to play a central role in initiating and regulating adipocyte differentiation [Endocrinology 135, 798-800, (1994)] and energy homeostasis, [Cell, 83, 803-812 (1995); Cell, 99, 239-242 (1999)]. PPARγ agonists would stimulate the terminal differentiation of adipocyte precursors and cause morphological and molecular changes characteristic of a more differentiated, less malignant state. During adipocyte differentiation, several highly specialized proteins are induced, which are being involved in lipid storage and metabolism. It is accepted that PPARγ activation leads to expression of CAP gene [Cell biology, 95, 14751-14756, (1998)], however, the exact link from PPARγ activation to changes in glucose metabolism and decrease in insulin resistance in muscle has not been clear. PPARα is involved in stimulating β-oxidation of fatty acids [Trends Endocrine. Metabolism, 4, 291-296 (1993)] resulting in plasma circulating free fatty acid reduction [Current Biol., 5, 618-621 (1995)]. Recently, role of PPARγ activation in the terminal differentiation of adipocyte precursors has been implicated in the treatment of cancer. [Cell, 79, 1147-1156 (1994); Cell, vol. No., 377-389 (1996); Molecular Cell, 465-470 (1998); Carcinogenesis, 1949-1953 (1998); Proc. Natl. Acad. Sci., 94, 237-241 (1997); Cancer Research, 58, 3344-3352 (1998)]. Since PPARγ is expressed in certain cells consistently, PPARγ agonists would lead to nontoxic chemotherapy. There is growing evidence that PPAR agonists may also influence the cardiovascular system through PPAR receptors as well as directly by modulating vessel wall function [Med. Res. Rev., 20 (5), 350-366 (2000)].
PPAR α agonists have been found useful in the treatment of obesity (WO 97/36579). Dual PPAR α and γ agonists have been suggested to be useful for Syndrome X (WO 97/25042). PPAR γ agonists and HMG-CoA reductase inhibitors have exhibited synergism and indicated the usefulness of the combination in the treatment of atherosclerosis and xanthoma (EP 0753 298).
Leptin is a protein when bound to leptin receptors is involved in sending satiety signal to the hypothalamus. Leptin resistance would therefore lead to excess food in-take, reduced energy expenditure, obesity, impaired glucose tolerance and diabetes. It has been reported that insulin sensitizers lower plasma leptin concentration [Proc. Natl. Acad. Sci. 93, 5793-5796 (1996): WO 98/02159)].
A number of compounds have been reported to be useful in the treatment of hyperlipidemia, hypercholesterolemia and hyperglycemia [U.S. Pat. Nos. 5,306,726, 5,985,884, 6,054,453, EP 90 3343, PCT publications Nos. WO 91/19702, WO 94/01420, WO 94/13650, WO 95/03038, WO 95/17394, WO 96/04260, WO 96/04261, WO 96/33998, WO 97/25042, WO 97/36579, WO 98/28534, WO 99/08501, WO 99/16758, WO 99/19313, WO99/20614, WO 00/23417, WO 00/23445, WO 00/23451].
A few β-aryl-α-hydroxypropanoic acids, their derivatives, and their analogs have been reported to be useful in the treatment of hyperglycemia and hypercholesterolemia. Some of such compounds described in the prior art are outlined below:    1. U.S. Pat. No. 5,306,726 and U.S. Pat. No. 5,089,514 disclose several 3-aryl-2-hydroxypropionic acid derivatives of general formulae (II) and (III) as hypolipidaemic and hypoglycemic agents. Examples of these compounds are shown in the formulae (IV) and (V).     2. International Patent Applications, U.S. Pat. No. 6,166,049 and WO 96/04260 disclose compounds of general formula (VI) wherein, Ra represents 2-benzoxazolyl or 2-pyridyl and Rb represent CF3, CH2OCH3 or CH3. A typical example is (S)-3-[4-[2-[N-(2-benzoxazolyl)N-methylamino]ethoxy]phenyl]-2-(2,2,2-trifluoro ethoxy)propanoic acid (VII).     3. International patent applications, WO 94/13650, WO 94/29302, U.S. Pat. No. 6,048,883, WO 95/17394 and WO 97/31970 disclose the compounds of general formula (VIII) wherein,A1—X—(CH2)n—O—A2—A3—YR2  (VIII)      A1 represents aromatic heterocycle moiety, A2 represents substituted benzene ring and A3 represents moiety of formula (CH2)m—CH—(OR1), where R1 represents alkyl groups, m is integer of the range of 1-5; X represents substituted or unsubstituted N; Y represents C═O or C═S and R2 represents OR3 where R3 may be hydrogen, alkyl, aralkyl, or aryl group and n is integer in the range of 2-6. An example of these compounds is shown in formula (IX).     4. International patent application, WO 00/23,445, WO 00/23,417 and WO 00/23,451 disclose cyclic compounds of the general formula (X) useful in treatment of diabetes and obesity. A typical example of these compounds is shown formulae (XI) and (XII).     5. International patent application, WO 99/08501 and WO 97/3197707, disclose cyclic compounds of the formulae (XIII) and (XIV) active as PPAR-gamma agonist. A typical examples of these compounds is shown formulae (XV) and (XVI).     6. U.S. Pat. No. 6,054,453 and WO 99/16758 reports compounds of general formulae (XVII), (XVIII), which reduce glucose, cholesterol and triglycerides exemplified by compounds of formula (XIX).     7. WO 99/19,313, U.S. Pat. No. 6,130,214 and WO 99/38850 reports compounds of general formula (XX) and (XXI) and (XXII) which reduce glucose, cholesterol and triglycerides. 